The Goodwills by us are ridiculous...anything that's remotely of value gets put in the glass case with an inflated price tag. The 10,000 copies of Madden 200X, Guitar Hero and Barbie Horse Adventure get put on the bookshelf with the DVDs. Last year I saw a $25 copy of Mario/Duck Hunt loose.
CRTs were about the only things that kept me going back to Goodwill, and unfortunately that's gone as well.
I've actually had much better luck with Church-affiliated thrifts like St. Vincent and small local ones. My best (and just about only) haul ever was a demo kiosk Yoshi's Island cart, Crystalis for the NES, and 4 NES Color Dreams carts, all for like $5.